With the development of communication technologies, a mobile communication system has been evolved into a System Architecture Evolution (SAE) system. FIG. 1 is a schematic diagram illustrating the structure of a conventional SAE system. As shown in FIG. 1, the SAE system includes an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) 101 and a core network at least including a Mobile Management Entity (MME) 105 and a Subscriber Gateway (S-GW) 106. The E-UTRAN 101 is configured to connect User Equipment (UE) to the core network and includes at least one evolved Node B (eNB) 102 and at least one Home eNB (HeNB) 103. The E-UTRAN 101 may further include a HeNB GW 104. The functions of the MME 105 and the S-GW 106 may be implemented by one module or implemented separately. eNBs 102 are connected to each other through an X2 interface, and each eNB102 is connected to the MME 105 and the S-GW 106 respectively through an S1 interface. The HeNB 103 is directly connected to the MME 105 and the S-GW 106 respectively through the S1 interface, or the HeNB 103 is connected to the HeNB GW 104 through the S1 interface, and then the HeNB GW 104 is connected to the MME 105 and the S-GW 106 respectively through the S1 interface.
In the early phase of establishing the SAE system or during the operation of the SAE system, a mass of human and material resources are needed to configure and optimize parameters of the SAE system, especially radio parameters, so as to guarantee that the SAE system has satisfying coverage, capacity, mobile robustness, mobile load balance and access speed of UE. In order to save the human and material resources during the operation of the SAE system, a self-optimization method of the SAE system is provided. In a self-optimization process, the configuration of eNB or HeNB is self-optimized according to a current state of the SAE system. Hereinafter, the eNB and the HeNB are called an eNB collectively, and the self-optimization method of the SAE system is illustrated.
FIG. 2 is a schematic diagram illustrating a principle of self-optimizing the SAE system. As shown in FIG. 2, after the eNB is powered or accesses the SAE system, the eNB performs self-configuration. The self-configuration process includes basic configuration and initial radio parameter configuration of the eNB. The basic configuration of the eNB includes configuring an IP address of the eNB, checking Operation, Maintenance and Management (OA&M), verification between the eNB and the core network, detecting a HeNB GW to which the eNB belongs if the eNB is a HeNB, and downloading software and operation parameters of the eNB to configure the eNB. The initial radio parameter configuration is implemented according to experiences and simulation. Because the performance of each eNB in the SAE system may be influenced by the environment of a region where the eNB is located, the eNB needs to perform initial configuration of adjacent cell list and initial configuration of load balance according to the initial radio parameter configuration of the region where the eNB is located. After the self-configuration process, many parameters configured by the eNB are not optimal. In order to make the SAE system have better performance, the configuration of the eNB needs to be optimized or adjusted, which is called self-optimization of mobile communication system. The configuration of the eNB may be optimized and adjusted through controlling the eNB by background OA&M. there may be a standard interface between the OA&M and the eNB. The OA&M sends a to-be-optimized parameter to the eNB (which may be an eNB or a HeNB) through the interface, and then the eNB optimizes a self-configured parameter according to the to-be-optimized parameter. Of cause, the eNB may optimize the parameters by itself. That is, the eNB detects that its performance needs to be optimized, and then optimizes or adjusts its corresponding parameters. The optimizing or adjusting the configuration of the eNB includes the self-optimization of adjacent cell list, the self-optimization of coverage and capacity, self-optimization of mobile robustness, self-optimization of load balance and the self-optimization of Random Access Channel (RACH) parameter.
The basic principle of self-optimization of load balance includes: adjacent cells exchange load information with each other, a source cell hands over UE served by the source cell to an adjacent destination cell when load balance is needed, and then the destination cell performs access control. When load balance is needed, the source cell may request the destination cell to change handover or cell reselection parameters of the destination cell. The source cell sends the destination cell a relative change value to be triggered by handover. The relative change value to be triggered by handover is a specific shift value of a cell triggering a handover preparing process. The destination cell accepts the request of the source cell, and the source cell considers a response value before the UE served by the source cell is handed over.
The conventional method may be applied to the handover between intra-frequency cells in a Long Term Evolution (LTE) system. However, if the above method is applied to the handover between inter-frequency cells in the LTE system or the handover between cells of different access systems, some problems will be caused.
A first problem is described as follows. For mobility between different frequencies or different Radio Access Technologies (RATs), there are no cell specific handover or cell reselection parameters. If the source cell changes mobile parameters for handing over to a certain frequency or RAT, mobile parameters to all neighbor cells that works on the frequency or RAT are influenced. However, a method for processing this case has not been provided in the prior art.
A second problem is described as follows. The handover or measurement mechanism between different frequencies or different access systems is different from the handover between intra-frequency cells in the LTE system. After a destination eNB receives a change request parameter from the source cell, the destination eNB does not know what is requested to be changed. If the destination eNB does not know which parameter is requested to be changed, the destination eNB does not know how to operate and may adopt a contrary operation. In this way, not only the automatic adjustment of mobile parameter cannot achieve an effect, but also a contrary function may occur, which makes system performance worse.